WASHINGTON — The top U.S. military commander told Congress on Thursday that President Barack Obama's proposal to draw down 33,000 troops from Afghanistan was riskier and more aggressive than he'd proposed.

Appearing before the House Armed Services Committee, Navy Adm. Mike Mullen, the chairman of the Joint Chiefs of Staff, said Obama's plans were "more aggressive and incur more risk than I was originally prepared to accept."

Despite that, however, Mullen said he was comfortable with the president's decision, announced in a televised address Wednesday night, to bring 10,000 troops home this year and to withdraw by next summer all 33,000 of the service members who formed the "surge" he announced in December 2009.

"Only the president, in the end, can really determine the acceptable level of risk we must take. I believe he has done so," Mullen said.

Army Gen. David Petraeus, the top commander of U.S.-led forces in Afghanistan, later echoed Mullen's comments during his confirmation hearing to be the new CIA director.

Testifying before the Senate Intelligence Committee, Petraeus said that Obama had settled on "a more aggressive formulation in terms of the timeline than what we had recommended."

He added that the president had to take into consideration other points of view "and ultimately the decision has been made and...ultimately I support that."

Members of the House committee, many of whom said they were dubious about Obama's plan and its likelihood of success, asked Mullen which aspects were risky.

"It is a risk to the overall mission," Mullen said. "I think it's increased risk across the board, but it's manageable risk."

The president said his military strategy was working, that the Taliban and al Qaida were weakening and that Afghan security forces would be ready to fill the breach left by departing U.S. troops. Once complete, the drawdown would leave 68,000 American troops in Afghanistan.

Top military commanders had proposed a slower withdrawal, calling the gains fragile and reversible. Privately, Pentagon commanders are worried about the overall strategy, saying they aren't confident that Afghan security forces can secure their country.

Meanwhile, Afghans who've backed the U.S. effort in Afghanistan worry that the Taliban will regain control and retaliate against them.

"No commander ever wants to sacrifice fighting power in the middle of a war," Mullen told the committee. "And no decision to demand that sacrifice is ever without risk."

Also on Thursday, Secretary of State Hillary Clinton told the Senate Foreign Relations Committee that the Obama administration thinks that "a political solution" to the Afghan war "is possible."

She confirmed that U.S. officials have had "very preliminary outreach to members of the Taliban," which she said was "not a pleasant business" but was required to bring peace to Afghanistan.

Clinton apparently was referring to at least three meetings that a senior U.S. diplomat has had with Tayyeb Agha, a former personal assistant to Mullah Mohammad Omar, the Afghan Taliban leader, who's thought to be living in the southwestern Pakistani city of Quetta.

U.S. officials, however, have indicated that there's been no apparent progress toward convening negotiations on a peace agreement, and serious questions remain about how much influence Agha still wields with Omar and his leadership council, known as the Quetta Shura.